1. FIELD OF THE INVENTION
The present invention relates to a method of and apparatus for controlling the path of a robot having a position detecting means for detecting the position of a work.
2. DESCRIPTION OF THE PRIOR ART
In the field of industrial robots for performing tasks such as welding, sealing or the like, there has been proposed to provide a position detecting means on the robot so that the robot can detect any change in the shape of the work or the position of the work relatively to the robot and perform the task automatically and correctly while correcting the content of the instruction in accordance with the result of the detection.
FIG. 1 shows a conventional system for achieving a task such as welding or sealing by means of a robot. Namely, a plate W.sub.2 having a hook-shaped plan is placed on a horizontal plate W.sub.1, and welding or application of an adhesive is achieved by a robot along the inner juncture line between the plates W.sub.1 and W.sub.2, i.e. along the lines between points a and b, b and c, c and d.
Points P.sub.1 to P.sub.6 are determined as positions for making the detection of the work by means of the position detection means. The detection of the working positions is made by moving the detection means by the robot in the direction of arrows f.sub.1 to f.sub.17. The position detection means detects the plate W.sub.2 when it is moved in the direction of arrows f.sub.1, f.sub.4, f.sub.7, f.sub.10, f.sub.12 and f.sub.16 and upon receipt of a predetermined signal, moved back along the arrows f.sub.2, f.sub.5, f.sub.6, f.sub.11, f.sub.14 and f.sub.17. Therefore, the points P.sub.1 to P.sub.6 of detecting operation have to be determined to fall, even when the positions of the plates W.sub.1 and W.sub.2 are fluctuated relatively to the robot, within the range of straight lines between points a and b, b and c and c and d. The points P.sub.1 and P.sub.6 of the position detecting operation have to be determined such that the plate W.sub.2 can be detected without fail when the position detection means is moved in the directions of arrows f.sub. 1 and f.sub.16. Therefore, at the points P.sub.1 and P.sub.6, the detecting operation is inevitably made for points spaced away from the points a and b.
The points P.sub.1 ' to P.sub.6 ' on the work corresponding to respective points P.sub.1 to P.sub.6 are determined by a calculation from the output of a posture detection means of the robot when the position detection means provides a specific signal. The points b and c are determined by calculating the points of intersection between the line interconnecting points P.sub.2 ' and P.sub.4 ' and the line interconnecting points P.sub.1 ' and P.sub.2 ' or the line interconnecting points P.sub.3 ' and P.sub.6 '.
Therefore, the welding or sealing between the point P.sub.1 ' and point b, point b and point c, and point c and point P.sub.6 ' can be achieved by moving the robot while making a linear interpolation of the object of the path control.
Conventionally, however, it has not been possible to effect an automatic work such as welding, sealing or the like in the region between point a and point P.sub.1 ' and the region between point P.sub.6 ' and point d. In these regions, therefore, the work had to be accomplished by a manual work which is quite troublesome and time consuming.